U.S. patent number 4,702,415 [Application Number 06/652,740] was granted by the patent office on 1987-10-27 for aerosol producing device.
This patent grant is currently assigned to Vortran Corporation. Invention is credited to Nathaniel Hughes.
United States Patent |
4,702,415 |
Hughes |
October 27, 1987 |
Aerosol producing device
Abstract
An apparatus and method are disclosed for applying an active
ingredient as an aerosol. A transducer (22) for creating an aerosol
includes a propellant inlet (96) and a chamber defined by at least
one chamber wall (128) confluent with the propellant inlet. A bluff
body (112) is provided for creating at least one vortex (152) in
the chamber when the propellant enters the propellant inlet in a
supersonic flow condition. An orifice (118, 146) spaced apart from
the bluff body and separated therefrom by the chamber wall is
provided for creating an exiting vortex (154).
Inventors: |
Hughes; Nathaniel (Palm
Springs, CA) |
Assignee: |
Vortran Corporation (Culver
City, CA)
|
Family
ID: |
57793807 |
Appl.
No.: |
06/652,740 |
Filed: |
September 18, 1984 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
555703 |
Nov 28, 1983 |
4635857 |
Jan 13, 1987 |
|
|
Current U.S.
Class: |
239/8;
128/200.18; 239/11; 239/370; 239/434; 261/78.2; 128/200.21;
239/338; 239/426; 239/589.1; 261/DIG.65 |
Current CPC
Class: |
A61M
15/0015 (20140204); A61M 15/0088 (20140204); A61M
16/125 (20140204); A61M 11/005 (20130101); A61M
15/00 (20130101); A61M 15/009 (20130101); B05B
1/34 (20130101); B05B 7/0012 (20130101); B05B
7/066 (20130101); B05B 7/10 (20130101); B05B
7/168 (20130101); G01F 1/32 (20130101); A61M
15/0026 (20140204); A61M 16/101 (20140204); A61M
11/06 (20130101); A61M 15/0086 (20130101); A61M
2202/064 (20130101); A61M 2206/16 (20130101); A61M
2209/084 (20130101); Y10S 261/65 (20130101) |
Current International
Class: |
A61M
15/00 (20060101); B05B 7/16 (20060101); A61M
11/06 (20060101); A61M 011/06 () |
Field of
Search: |
;239/102,338,370,590,590.3,590.5,DIG.20,DIG.23,403,426,434,8,11,461,463,589.1
;128/200.18,200.21 ;261/DIG.65,78.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Metered-Dose Aerosol Administration", by Martin Tobin, MD (paper
presented at American Assn. of Respiratory Therapy 28th Annual
Convention and Exposition, Oct. 30-Nov. 2, 1982, New Orleans, La.),
pp. 16-20. .
"Aerosolized Drug Delivery Accessories", by A. J. Curie, S.
Ertefaie & J. J. Sciarra, Aerosol Age, Mar. 1984, pp.
24-26..
|
Primary Examiner: Kashnikow; Andres
Assistant Examiner: Forman; Michael
Attorney, Agent or Firm: Christie, Parker & Hale
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is copending with a related application entitled
"Single Inlet Prepackaged Inhaler", Ser. No. 652,754, filed Sept.
18, 1984, and is a continuation-in-part of an application entitled
"Atomizing Apparatus", Ser. No. 555,703, filed Nov. 28, 1983 now
U.S. Pat. No. 4,635,857, issued Jan. 13, 1987.
Claims
I claim:
1. A process for creating an aerosol characterized by the steps
of:
providing a propellant to an inlet of a transducer;
impacting the propellant on a bluff body to create at least one
vortex;
feeding the at least one vortex to an aperture spaced apart from
the bluff body;
producing a vortex through an orifice spaced apart from the bluff
body and separated from the bluff body by a wall preventing flow of
fluid along the bluff body to the orifice; and
incorporating an active ingredient into the propellant.
2. A transducer for creating an aerosol having an inlet and an
outlet portions, the transducer characterized by:
a single inlet tube having a first central axis;
a transducer body having a second central axis and to which the
tube is coupled and wherein the first central axis is normal to a
plane containing the second central axis;
a bluff body extending from one end of the transducer body
substantially to another end along the second central axis and
comprising a groove in an end adjacent the other end of the
transducer body extending from an interior surface portion of the
bluff body to the end thereof; and
a cylindrical lens portion adapted to be positioned substantially
within the other end of the transducer body and about the end of
the bluff body, the lens portion comprising:
a first cylindrical aperture comprising an upstream portion and
extending from an upstream portion of the lens portion to a
downstream portion through the center of the lens portion for
fitting the lens portion about the bluff body,
a first conically-shaped depression in the upstream portion
converging downstream-wise to the upstream portion of the
aperture,
a second conically-shaped depression in the downstream portion of
the lens portion diverging downstream-wise from the dowstream
portion of the aperture,
a second cylindrical aperture extending from the first depression
toward the second depression, and
a third cylindrical aperture extending from the second cylindrical
aperture to the first cylindrical aperture.
Description
TECHNICAL FIELD
This invention relates to devices for producing an aerosol and more
specifically to transducers for creating an aerosol.
BACKGROUND ART
Aerosol dispensers are generally well known in the art. These
devices utilize transducers which generally create a spray of an
active ingredient using a propellant. The resulting spray includes
oversized liquid particles with a significant forward velocity
which impact the surface or element being sprayed. The spray is
non-uniform and results in a non-uniform deposition of active
ingredient and consequent ineffective use of the active ingredient.
There is no device which could deliver an aerosol having particles
of a relatively small, uniformly consistent size. One type of
aerosol dispenser presently in use is anti-asthmatic medication
inhalers. In one such device, a 10-centimeter (4-inch) spacer was
attached to the inhaler in an attempt to provide uniform particle
size, which spacers produced a noncompact cumbersome inhaler. The
transducer alone, however, is still ineffective to produce an
aerosol having the desired characteristics.
U.S. Pat. No. 4,241,877 to Hughes shows a vortex generating device
in FIGS. 5A, 5B, and 6, wherein a gas and a liquid pass into a flow
passage together from an inlet. The mixture flows about a rod and
forms vortices thereabout and enters a bore along a portion of the
rod after which the mixture exits the device through a constricted
bore to a semispherical diverging outlet. The liquid is partially
atomized as it leaves the bore in the inlet and becomes fully
atomized as it leaves the semispherical diverging outlet in a
vortical gas stream. A device is also shown where a gas and liquid
under pressure are supplied together through an inlet member to a
transversely extending rod for formation of vortices. The vortices
flow in a direction coaxial with the rod to a constricted outlet
bore and to a semispherical diverging outlet. The vortices also
flow along auxiliary passages toward the constricted bore portion
to combine with the previously-mentioned coaxial flowing
vortices.
The Hughes '877 device is suitable for relatively high mass flow
rates, but would not be suitable for use with propellant-charged
canisters containing a relatively low
propellant-to-active-ingredient ratio. With such canisters, it is
desirable to minimize the proportion of propellant in each shot
while maximizing the concurrent output of the active ingredient.
Furthermore, it would be relatively difficult and expensive to
manufacture a device as indicated in the Hughes '877 patent and
still provide the required aerosol characteristics in conjunction
with the propellant-charged canister.
The present invention overcomes these deficiencies in the prior
devices. The device provides an aerosol having particles which are
uniform in size regardless of the variation in range of pressure
provided through the propellant in the canister. This result
inheres even with low propellant-to-active-ingredient ratios and
low mass flow rates.
The present invention is useful in a number of applications where a
relatively small concentration of propellant and active ingredient
is used in applying the active ingredient. The invention may be
utilized in aerosol medication inhalers, paint sprayers, topical
medication applications, hairspray, deodorant, lubricants and other
aerosol applications.
The present invention due to its unique operation on miniscule
amounts of gas or liquified propellant permits a unique capability
when used in conjunction with the apparatus disclosed in the
copending applications CP&H Ser. No. 652,753 filed 9/18/84 and
Ser. No. 555,703 filed 11/28/83 as a nebulizer permits operation at
extremely low flow of oxygen or propellant namely from 0-5 liters
per minute. This capability is of extreme importance in hospital
and home therapy. Oxygen is toxic at high levels in 100% by volume
concentration. Oxygen is also costly and at high levels makes for
difficult patient ingestion of drugs.
DISCLOSURE OF THE INVENTION
An apparatus and method are disclosed for applying an active
ingredient as an aerosol. A transducer for creating an aerosol
having an inlet and an outlet portions includes a propellant inlet
and a chamber defined by at least one chamber wall confluent with
the propellant inlet. Means are provided for creating at least one
vortex in the chamber when the propellant enters the propellant
inlet in a supersonic flow condition. Means spaced apart from the
vortex creating means and separated therefrom by the chamber wall
is provided for creating an exiting vortex.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side-sectional view of a metered-dose inhaler using a
single-inlet transducer assembly for creating an aerosol according
to the present invention;
FIG. 2 is a schematic and side-sectional view of the transducer
assembly shown in FIG. 1;
FIG. 3 is a front elevation view of the transducer assembly of FIG.
2;
FIG. 4 is a side section of a lens element for use in the
transducer assembly of FIG. 3 taken along lines 4--4 of FIG. 3;
FIG. 5 is a side-sectional view of a portion of the inhaler of FIG.
1 showing two expansion chambers;
FIG. 6 shows an alternative embodiment of the device of FIG. 1 with
an additional screen;
FIG. 7 shows a schematic of a transverse cross section of the
transducer assembly of FIG. 2 showing shockwaves and vortices;
FIG. 8 shows a resonant screen for use in the inhaler of FIG.
1;
FIG. 9 shows a front elevation view of a body portion of the
inhaler;
FIG. 10 shows an alternative embodiment of the transducer assembly
of FIG. 2;
FIGS. 11 and 12 show adapters for the output portions of the
inhaler; and
FIGS. 13, 14 and 15 show alternative embodiments of the transducer
assembly of FIG. 10.
MODES FOR CARRYING OUT THE INVENTION
It will be understood that the description herein of the apparatus
and its use includes a description of the method for producing an
aerosol. The description of the transducer is provided in relation
to its use in conjunction with a medication inhaler. However, the
application of the transducer is not to be limited to its use with
a medication inhaler but is useful for producing aerosols for other
applications.
FIG. 1 shows a transducer assembly 22 being used in conjunction
with a medication inhaler 20. The transducer assembly 22 includes a
propellant inlet 96 and a chamber defined by at least one chamber
wall 128 and confluent with the propellant inlet 96. Means in the
form of bluff body 112 is provided for creating at least one vortex
152 in the chamber when the propellant enters the propellant inlet
in a supersonic flow condition. Means in the form of an orifice
defined by a groove 118 and surface 146 is provided spaced apart
from the vortexcreating means and separated therefrom by the
chamber wall 128 for creating an exiting vortex, indicated
generally at 154.
The inhaler 20 of FIG. 1 includes a first body portion 38 for
accepting and retaining the container 24 and for partially
enclosing the transducer assembly 22. The container 24 has a
structure and function similar to metered dose containers generally
known in the art. The first body portion 38 is generally shaped in
the form of an elbow having a hollow, cylindrical, generally
upwardly extending vertical arm 40 and a hollow, cylindrical,
generally forwardly extending (with respect to the remainder of the
inhaler 20) horizontal arm 42. (The directional terms used herein,
such as horizontal, vertical and upward are intended to be used for
reference to the drawings only and are not to be construed as a
limitation on the structure or function of the device.) The
vertical arm 40 extends along a verticle axis 44. The front half 46
of the verticle arm 40 extends vertically substantially all the way
to the horizontal arm 42, except for a slot, rectangular in frontal
view, for allowing insertion of the transducer (described below).
The rear half 48 of the vertical arm 40 extends vertically downward
to a bend 50 forming the back half and the bottom portion of
horizontal arm 42.
Horizontal arm 42 extends from the bend 50 substantially
horizontally, as shown in FIG. 1, about a horizontal axis 56. The
vertical axis 44 is normal to a plane containing the horizontal
axis 56. The horizontal arm 42 is substantially right circular
cylindrical in vertical transverse cross section, as shown in FIG.
9. The horizontal arm 42 extends forward about and past the
transducer assembly 22 (in assembled form) to the end 58 of the
first body portion 38. The outer surface of the horizontal arm 42
terminates flush with the outer surface of second body portion
60.
The interior surface of horizontal arm 42 is also substantially
right circular cylindrical in vertical transverse cross section and
includes an end plate 60a at the left end, as seen in FIG. 1, of
the horizontal arm 42. A key-way 60b (FIG. 9) is cut in the top
surface of the cylindrical portion of horizontal arm 42 for guiding
and retaining the inlet of the transducer assembly, to be described
more fully below, as the assembly is placed in the horizontal
arm.
The first body portion 38 is formed generally such that it is
compact and partly provides protection to the transducer assembly
22 and to the container 24. The external dimensions of the first
body portion 38, along with second body portion 60 are such that
the inhaler 20 is compact and easily fits in the hand and may fit
into a pocket. The first body portion 38 along with the second body
portion 60 are preferably made of polypropylene but may be made of
other medical grade organic polymers providing structural support
and desirable surface qualities after molding.
The second body portion 60 is for retaining and positioning the
transducer assembly 22 and for changing the flow conditions of the
aerosol subsequent to aerosol production in the transducer
assembly. The latter function depends on the interior design of the
second body portion 60.
The second body portion 60 has a rear portion whose outside and
inside diameters are approximately one-half the outside and inside
diameters, respectively, of the immediately adjacent forward
portion. The rear portion extends within and mates with the
interior surface of horizontal arm 42. The upper surface has a
horizontally extending "U"-shaped cut (as viewed from above) made
from the edge of a rear portion therein for accommodating the
vertical inlet (to be described below) of the transducer assembly
22. The remainder of the rear portion is substantially cylindrical
in vertical transverse cross section and extends from the rear
portion of transducer assembly 22 to the remainder of second body
portion 60. Midway along the outer surface of the second body
portion is a perimetrical flanged surface 61 for mating with the
end 58 of the horizontal arm. At the top, as viewed in FIG. 1, a
rectangular key 61a extends generally horizontally rearward from
the flanged surface 61 to mate with the key-way 60b (FIG. 9) in the
top of the horizontal arm.
As shown in FIG. 5, the second body portion extends from the rear
end 62 having a preferred inside diameter indicated generally at 64
of approximately 0.467 inch to the end 66 of the first expansion
chamber wherein the inside diameter, indicated generally at 68 is
preferably 0.480 inch. At the end of the first expansion chamber 30
in the first downstream portion 32 the inside dimensions of the
second body portion 60 increase to form a diverging conical portion
72 wherein the inside diameter 74 of the second body portion is
increased to preferably 0.940 inch. The angle 76 of the diverging
conical portion 72, from the horizontal is approximately
60.degree.. The diverging conical portion 72 and the remainder of
the second body portion 60 form a second expansion chamber 78. The
outside dimensions of the second body portion 60 are generally
designed for structural integrity and compactness secondarily to
the inside dimensions discussed above. The inside length of the
first expansion chamber 32 is preferably 1.230 inch, and the inside
length of the second expansion chamber from the end of the first is
1.273 inch.
As shown in FIG. 1, the first and second body portions 38 and 60,
respectively, are joined to form the exterior housing defining the
inhaler 20. The key 61a coupling the first and second body portions
at the top of the horizontal arm 42 generally prevents rotation of
the first body portion with respect to the second body portion. The
mutually adjacent surfaces of the first and second body portions
may be bonded by ultrasonic or sonic welding to provide an airtight
seal for preventing entrainment of air and preventing rotation of
the two portions with respect to each other.
As shown in FIG. 1, a vapor screen net or resonant screen 80 (FIG.
8) is positioned adjacent the outside horizontal rim 82 of the
second body portion 60 forming the second expansion chamber 78. The
resonant screen 80 is retained in place against the rim 82 by a
screen-retaining rim cap 84. The rim cap 84 is preferably
ultrasonically welded to the second body portion 60 to prevent
removal of the cap and resonant screen 80. The screen is preferably
formed of a nylon lattice having an extreme diameter of 0.980 inch
and a square lattice opening dimension of 0.060 inch.times.0.060
inch. Each lattice member is preferably 0.012 inch across the face
and 0.024 inch deep from one face of the screen to the other. The
outside diameter of the horizontal rim or lip of the second body
portion is also preferably 1.020 inch for retaining the resonant
screen in conjunction with the rim cap 84.
Alternatively, as shown in FIG. 6, the resonant screen 80 may have
a diameter of 0.910 inch and bonded to a frame 85 having an outside
diameter of 1.010 inch. The bonded screen is then placed on the
inside of the second expansion chamber and bonded thereto. The
resonant screen and frame are positioned in the end of the second
expansion chamber such that the outside surface of the resonant
screen is flush with the rim of the second expansion chamber.
A cap 86 may be provided anchored around part of the second body
portion 60 for capping the end of the inhaler at the second body
portion 60 for protecting the resonant screen 80 and for preventing
entry of foreign matter. The cap 86 may be made of nylon.
The transducer assembly 22 will now be described. The outside
dimensions of transducer assembly 22 to be used with the inhaler
are chosen so that the assembly is retained in and held by the
interior walls of the second body portion 60 at the rear portion
thereof. The joinder of the two is preferably a snap-in or snug
fit. The inlet 96 of transducer assembly 22 is placed in the
"U"-shaped key in the rear portion of second body portion 60. The
remainder of the rear portion of second body portion 60
substantially surrounds the sidewalls of transducer assembly 22.
The back edge 98 of the transducer assembly 22 is positioned
adjacent the end plate 60a of the horizontal arm. The transducer
assembly 22 is held by the key portion of second body portion 60
and is substantially surrounded by second body portion 60. For
other applications of the transducer, suitable means for holding or
mounting the transducer may be used.
Considering the transducer assembly 22 in more detail with respect
to FIGS. 2-4, the transducer assembly 22 is substantially right
circular cylindrical in external dimension and includes a
vertically oriented inlet 96 previously mentioned. The inlet 96 is
a single fluid inlet oriented about the vertical axis 44 for
accepting the nozzle 26, the medicated mixture from the nozzle 26
after actuation and for introducing the fluid to the remainder of
the transducer assembly 22. The rear surface of the inlet 96
extends vertically downward to the upper surface 100 of the
transducer body 102. The flat rear surface 98 is substantially
circular and closes the rear portion of the transducer body
102.
The front portion of the inlet 96 extends vertically downward to
the upper surface 100 of the transducer body 102. The transducer
body 102 extends along the horizontal axis 58. The exterior portion
of the transducer body 102 terminates at a forward circumferential
rim 106. The outside dimensions of the transducer body 102 are
formed so as to provide an airtight fit with the inside surfaces of
the second body portion 60 which will enclose the transducer body.
This prevents rotation of the transducer assembly with respect to
the second body portion 60 and prevents entrainment of air during
operation of the inhaler. The transducer assembly, including the
lens portion to be described below, is preferably formed from
polypropylene.
The inlet 96 includes a bore 107 adjacent the interior of the
transducer body 102 and a counterbore 107a having an inside
diameter 108 for accepting the nozzle of the canister.
The inside diameter of the bore 107 and the length of bore 107 are
dimensioned such that the fluid ejected from the nozzle of the
canister is optimized for adequate fluid expansion and flow to the
interior of the transducer body. The inside diameter of bore 107 is
preferably 0.075 inch, and the length is preferably 0.0825 inch The
inside diameter 108 is dimensioned for the appropriate size of the
nozzle 26.
The inlet terminates in an aperture 109 opening into the interior
of the transducer body 102. The transducer body is formed in part
by the rear inside surface 109a forming a substantially circular
face at the extreme upstream end of the transducer body 102 and by
the circumferential surface 110, which surface is oriented
equidistant about the horizontal axis 58. Concentric with the
circumferential surface 110 and coaxial with the horizontal axis 58
is a bluff body 112 formed substantially from a right circular
cylinder whose axis is the horizontal axis 58 and against which the
mixture is impacted for creating vortices in the transducer body.
The upstream portion of bluff body 112 is formed from, or molded
with, the center of the rear inside surface 109a of the transducer
body 102. Preferably, the surface of the junction of the two is
curved and has a radius of curvature. The inside diameter of the
circumferential surface 110 is preferably 0.312 inch.
The circumferential surface 110 terminates opposite the rear inside
surface 109a in a second circumferential surface 114 for
surrounding and holding the lens. The inside diameter of the second
circumferential surface 114 is preferably 0.375 inch. The second
inside circumferential surface 114 extends from the termination of
the circumferential surface 110 to the transducer body rim 106. The
distance from the termination of the circumferential surface 110 to
the body rim is preferably 0.176 inch.
At the top of the second circumferential surface 114 is molded a
substantially hemi-cylindrical woodruff key 116 for orienting and
retaining the lens within the transducer body 22. The key
preferably has a radius of 0.025 inch and extends substantially the
length of the second circumferential surface 114.
The bluff body 112 extends beyond the termination of the
circumferential surface 110 almost to a point in a plane defined by
rim 106, preferably to within 0.013 inch of the plane of rim 106.
The length of the bluff body 112 extends from the rear inside
surface 109a a distance of preferably 0.366 inch.
In the bottom surface of the bluff body, on the surface opposite
the woodruff key 116, a groove 118 is provided for forming an
orifice for creating supersonic vortex flow from the transducer
assembly. The groove preferably extends 0.040 inch to the end of
the bluff body and has a radius of curvature of 0.012 inch.
A cylindrical lens portion 120 is seated in the volume defined by
the second circumferential surface 114 and mounted on the portion
of bluff body 112 surrounded by the second circumferential surface
114. The cylindrical lens portion 120 is for focusing and
condensing vortically flowing fluid developed by the bluff body
112.
The lens has an outside circumferential face 122 dimensioned to
correspond in part with the second circumferential surface 114 of
the transducer body 102. The face 122 is dimensioned to form a
tapered surface at the upstream end thereof to facilitate an easy
but tight, snap-in fit with the transducer body. Additionally, the
cylindrical lens portion 120 is provided with a groove 124 in its
outside circumferential face corresponding to the woodruff key 116
of the transducer body 102. The diameter of the groove is
preferably 0.056 inch. The outside circumferential face 122 is
preferably dimensioned such that when placed within the second
circumferential surface 114, the cylindrical lens portion 120 is
retained by the tight fit of the transducer body 102 and the lens
portion 120. If desired, an airtight fit may be provided by
ultrasonic or sonic welding.
The cylindrical lens portion 120 is provided with an aperture 126
having an inside diameter corresponding to the outside diameter of
the bluff body 112. In order to form a good fit between the lens
portion and the transducer body, the outside diameter of the bluff
body 112 is preferably 0.072 inch, and the inside diameter of the
lens aperture is 0.072 inch. Aperture 126 is formed symmetrically
about horizontal axis 58.
A first conically shaped depression 128 is formed in the upstream
surface of cylindrical lens portion 120, converging inward toward
the aperture 126 and serves to focus the vortices. The maximum
diameter of the depression 128 at the upstream edge 130 is
preferably 0.322 inch and substantially equivalent to the inside
diameter of the circumferential surface 110. The surface of the
cone forms an angle of about 57.degree. with the horizontal axis
58. The depression terminates at the aperture 126 having a diameter
of 0.072 inch. The height of the conical depression from the
upstream edge 130 to the upstream edge of aperture 126 is
preferably 0.081 inch.
A second conically-shaped depression 132 extends from the
downstream edge of aperture 126 along horizontal axis 58 to the
downstream edge 134 of the lens portion 120. The second depression
132 diverges such that the conical surface preferably forms a
45.degree. angle with the horizontal axis 58 for enhancing
formation of a large vortex having supersonic flow and a
subatmospheric pressure region. The maximum diameter of the
depression is preferably 0.133 inch. The aperture 126 preferably
extends 0.084 inch along the cylindrical lens portion 120 such that
there is a cylindrical volume 136 beyond bluff body 112 before the
second conically depression 132 begins for focusing the vortices.
Preferably, the length of the cylindrical volume is 0.004 inch. The
inside diameter is the same as that of the aperture 126.
A second cylindrical aperture or conduit section 138 is formed in
the cylindrical lens portion 120 having an axis 140 extending
horizontally and parallel to horizontal axis 58 and is radially
offset from aperture 126. The second aperture is provided for
concentrating vortices developed at bluff body 112, and the
conically-shaped depression 128, and for transporting the flow to
the orifice formed by groove 118. The second cylindrical aperture
138 is preferably formed on the side of the bluff body opposite the
inlet 96 and on the same side as groove 118. Furthermore, the
aperture 138 is formed in the lens portion 120 180.degree. from the
woodruff key groove 124. The axis 140 is positioned 0.122 inch from
the horizontal axis 58. As a result, the upstream rim of the second
aperture is positioned entirely along the surface of the first
conically-shaped depression 128.
A third cylindrical aperture or conduit section 142 is formed in
the lens portion 120 extending from the outside circumferential
face 122 of the lens portion 120 radially inward to the aperture
126. The third cylindrical aperture 142 is oriented about a second
vertical axis 144 which preferably intersects and is at right
angles with the horizontal axis 58. Additionally, the horizontal
axis 140 preferably intersects and is perpendicular to the second
vertical axis 144. The third cylindrical aperture enhances the
vortical flow of the mixture due to its 90.degree. configuration
with respect to the second aperture 138 and further focuses the
flow of the mixture and transports it to the orifice. The second
vertical axis 144 is preferably 0.122 inch from the upstream edge
130 of the lens portion 120. The diameter of the third cylindrical
aperture 142 is preferably 0.060 inch. As a result, only a portion
of the third cylindrical aperture 142 opens into a portion of the
groove 118. The remainder of groove 118, specifically between
0.0065 and 0.0125 inch of groove 118, is enclosed within the
aperture 126. A nozzle or orifice is thereby formed in the final
portion of groove 118 as a result of the intersection of the
grooved cylinder with the circular aperture. Due to the circular
nature of the third cylindrical aperture 142 as it intersects
groove 118, the bottom surface 146 formed by the intersection of
the groove 118 and the third cylindrical aperture 142 appears as
indicated in FIGS. 2 and 3. Furthermore, the vertical sectional
view of the orifice formed by the intersection of the groove 118
with the lens portion 120 is as shown in FIG. 3 comprising two arcs
having different radii of curvature. Tests have been conducted
wherein the radius of the groove 118 is varied between 0.010 and
0.014 inch, and it has been determined that with the other
dimensions described, the optimum radius is 0.012.
The nozzle formed by the intersection of the groove 118 and the
third cylindrical aperture 142 is for focusing the fluid obtained
from the second cylindrical aperture 138 and third cylindrical
aperture 142 for ejection into the cylindrical volume 136 and
expansion into the second conically-shaped depression 132. The
nozzle forms a single, large vortex having supersonic flow and a
sub-atmospheric region. As described below, the nozzle produces the
vortex and assists in centralizing the vortex.
The downstream edge 134 is at the extreme downstream portion of the
lens 120. The remainder of the downstream portion of lens 120
extends outwardly and rearwardly, preferably at a 10.degree. angle
from the plane defined by the downstream edge 134, to the outside
circumferential face 122 of lens 120. The outside face 122 then
extends rearwardly to the forward circumferential rim 106 of
transducer body 102. The horizontal distance from the downstream
edge 134 to the outside circumferential face 122 is preferably
0.021 inch.
As would be apparent, the output of the transducer assembly can be
varied by varying the diameters of the various apertures and of the
groove. Furthermore, additional apertures may be provided for
providing a flow path to the groove 118. However, for flow regimes
developed with currently marketed canisters, the configuration of
FIG. 1 is preferred.
FIG. 6 shows a schematic of an alternative embodiment of the
inhaler 20, including a second resonant screen 148 for performing
substantially the same function of the first resonant screen 80 in
substantially the same way. Resonant screens 80 and 148 may be used
together or alone to achieve the desired flow characteristics.
The operation of the device will now be described with respect to
the Figures. The inhaler 20 is assembled as would be apparent to
one skilled in the art. The patient then places a container 24
having a mixture of propellant, active medication, and solvent in
an inverted fashion into the first body portion 38. The outlet port
of nozzle 26 then is confluent with aperture 92 (FIG. 3)
The staging chamber of container 24 is filled with the
appropriately metered dose of the mixer of propellant and the
medication. The patient then depresses the container relative to
the first body portion 38 so that the nozzle 26 is forced further
into the mouth of container 24. The interior port to container 24
is thereby sealed and the mixture contained in the staging chamber
is ejected under a pressure of between 30 and 50 pounds per square
inch, depending upon the particular container being used. The
volume of the staging chamber may be approximately 0.05 cubic
centimeters so that the total volume of the mixture of propellant
and medication is approximately 0.05 cubic centimeters.
As discussed in the '877 patent, the phenomenon of "cold boiling"
and/or the resultant atomization of the liquid in the
propellant-solvent mixture may occur when the injected mixture is
pressurized and then released into the inlet 96. Preferably, the
ratio of the gas pressure to the ambient pressure is greater than
the critical pressure ratio. For example, the pressure of the
mixture in the canister 24 may be approximately 50 pounds per
square inch, gage (psig). The propellant to liquid ratio may be
typically 30:1 and the volume of output per shot may be 0.05 cubic
centimeters.
As a result of the high propellant and liquid pressure, the flow of
gas is supersonic as it enters the inlet 96. The ejected fluid then
expands into the inlet 96. The fluid flows along the inlet 96
without further significant change in volume or velocity until
reaching the transducer body 102, where the mixture again goes
through expansion into the chamber defined by the rear inside
surface 109a, the circumferential surface 110 and the cylindrical
lens portion 120. The presence of bluff body 112 in front of the
supersonic gas gives rise to a standing shock wave indicated at 150
in FIGS. 2 and 7 and generation of a very large number of vortices
indicated at 152. The potential energy, i.e., static pressure, of
the gas supplied to the inlet is, in effect, partly converted to
kinetic energy--first as an increase in linear gas velocity, then
as shock waves, and finally as vortices in the flow passage. The
vortices are formed having axes generally parallel to the bluff
body 112. The vortices formed at the periphery of the bluff body
rotate en masse about axis 58. It is estimated that the pressure at
the bluff body 112 in the transducer body 102 is approximately
20-30 psig. The tiny vortices are formed at a rate of approximately
40,000-50,000 vortices per second, according to present estimates.
This is due to the high velocity of the flow and to the less
viscous flow of the propellant-liquid mixture. Formation of a
maximum number of vortices per unit time is preferred. The number
of vortices is proportional to the velocity and the area across
which the gas flows having a coefficient of drag.
Because of the pressure differential between the inlet 96 and the
first downstream portion 32 created by the pressurized flow of
fluid into the inlet, there is a pressure gradient toward the
second cylindrical aperture 138 in the first conically shaped
depression 128. The individual vortices are impinged on the second
aperture in the lens, causing compression thereof into a compressed
flow of vortices along the axis 142. The spinning vortices are then
forced by the pressure gradient into the third aperture 142 at
right angles to the second aperture and forced to flow to the
nozzle or orifice. The compacted vortices flow along the second
axis 144, impinge on the surface of groove 118, and change
direction again to flow at right angles to the second vertical axis
and along bottom surface 146. The vortices are thereby further
compressed and forced to flow through the cylindrical volume
represented at 136 and out to the second conically-shaped
depression 132. By this process, the vortices are squeezed or
compressed into the orifice with sudden expansion into the single
large vortex, represented at 154 in FIG. 2, through the second
conically shaped depression. The right angle turns through the
cylindrical apertures are believed to enhance the vortex effect in
the fluid flow.
The cylindrical apertures perform three functions. First, they
compensate for changes in operating conditions such as pressure and
flow rate, thereby making adjustments unnecessary in many cases.
Second, they enhance the vortex action in the device and thus its
atomizing power. Third, the cylindrical apertures contribute to the
formation of the aerosol from the outlet of the orifice for
creating the exiting vortex. These result in superior atomization
and/or higher sonic energy generation.
The vortex activity from the bluff body 112 to the final large
vortex 154 produces atomization of the liquid fraction in the
liquid-propellant mixture so that the medication contained in the
liquid fraction is atomized into a mist substantially containing
one to three micron-sized particles for entering the first
expansion chamber 30. It was found that one massive vortex was
formed by impinging the vortices on a rod and letting them escape
through an annular chamber. It is believed that once the large
number of tiny vortices are created from the bluff body, the
vortices can then be manipulated as desired to produce a given
result such as the single, large vortex 154.
The single large exiting vortex 154 is comprised of fluid flowing
at supersonic velocity due to the compression of the vortices
flowing through the orifice and due to the pressure difference
across the orifice being greater than the critical pressure. The
dose mixture went through a first supersonic flow regime, followed
by expansion and creation of vortices. The vortices were then
forced through the second and third apertures followed by a second
supersonic flow regime out of the orifice and expansion into one
large vortex. The pressure on the downstream side of the orifice is
approximately atmospheric. The exiting vortex represents a
conversion of a substantial amount of static energy to dynamic
energy. The vortex is spinning about an approximate center along
axis 58 even though the orifice is offcenter. The semicircular,
axially extending, wedge-shaped orifice, as seen in transverse
cross section, contributes to the centralizing effect on the single
vortex. Other configurations for an outlet orifice are
contemplated, but the arcuately sectioned circle shown in FIG. 3 is
preferred.
The design of the cylindrical lens portion 120 serves several
functions. One is to focus the vortex-containing fluid at the
orifice. The single cylindrical apertures 138 and 142 provide means
for impinging the tightly configured vortices developed about bluff
body 112 into focused flow and for increasing the pressure in the
flow channels of which the cylindrical apertures are comprised.
Because the flow rate in terms of mass times velocity is so low for
each dose from the canister, the flow passages must be small enough
to maintain the pressure gradient to the first expansion chamber 30
and to provide forward flow velocity for the vortices. The orifice
comprising groove 118 and bottom surface 146 is also designed to
provide these features and to provide vortex action and supersonic
flow, rather than merely squirting the fluid. The dimensions of the
orifice are preferably such as to create supersonic flow in the
fluid at the output for creating the single vortex, for providing
good atomization of the liquid portion of the mixture and to
provide a shock wave pattern in the single vortex which also serves
to enhance the atomization of the liquid.
A second factor which affects the configuration of the exiting
vortex is the propellant to liquid ratio. A limited amount of
energy is available for atomization to take place. It is important
to ration that energy while still obtaining the desired results. A
minimum amount of propellant is desired for a given volume of
liquid to maintain the supersonic nature of the exiting vortex, the
atomization characteristics thereof and the shock wave pattern
produced in the vortex during supersonic conditions. If the
relative quantity of propellant is significantly reduced, one or
more of these features of the exiting vortex would be affected.
However, the design of the transducer lens in the single inlet
transducer 22 and the relative proportion of propellant may be
adjusted as desired to maintain the desired characteristics of the
exiting vortex.
A second design consideration is the formation of the orifice by
the conjunction of groove 118 and the bottom surface 146 of the
cylindrical lens portion 120. There are various methods for
formation of such an orifice including formation of a hole in a
cylindrical plug using a laser process, and the formation of a hole
through various molding techniques. However, the formation of the
hole through molding techniques is often inaccurate and often does
not provide consistently reliable results. Molding techniques are
especially important where low cost, single inlet transducers of
the type shown in FIG. 2 are desired. To overcome the problems in
molding a transducer having an orifice with the small dimensions as
described above, the design illustrated in FIG. 2 was
developed.
As there shown, the small orifice is easily formed by the
conjunction of a cylindrical rod having a groove formed therein
with a circular aperture extending coaxial with the cylindrical rod
wherein the diameter of the aperture is equivalent to the diameter
of the cylindrical rod except for the groove cut therein. In this
form, a small orifice is formed and problems of tolerances between
the rod and aperture are eliminated and problems of variation in
dimensions of the orifice are minimized.
The single inlet transducer 22 can be accommodated for higher flow
rates and for larger variations in the propellant-to-liquid ratio
by changing the dimensions of the interior of the transducer and
the cylindrical apertures 138 and 142. Likewise, the groove and the
conically shaped depressions in the lens portion 120 may be
adjusted as required to produce the desired exiting vortex.
Furthermore, additional cylindrical apertures may be provided for
producing a symmetrical input to the first expansion chamber with
appropriate modification to the orifice. A separate orifice may be
provided for each radially extending cylindrical aperture. However,
it is preferred to have one set of cylindrical apertures on the
side of the bluff body 112 opposite the inlet to take full
advantage of the multiplicity of tightly wound vortices produced on
the downstream side of bluff body 112.
The single vortex includes a negative pressure zone at the center
thereof due to the pressure differential across the orifice being
greater or equal to the critical pressure ratio. It has been found
that there is enhanced atomization with the disclosed configuration
and minimization of deposition of moisture on adjacent surfaces and
on a target. It is believed that the particles are
electrostatically charged and, therefore, inhibit deposition and
recombination or condensation to form larger droplets.
The first expansion chamber provides for expansion of the vortex,
thereby reducing the velocity and, therefore, mean free path of the
individual medication particles and provides an area for confining
the atomized vapor. The expansion and slowing of the particles
inhibits condensation of the individual particles and deposition of
the particles along the chamber wall. The forward velocity of the
particles is transferred to increased random motion of the
individual particles. Additionally, it is believed that further
atomization of the particles may occur to a limited extent.
As the vortex continues to the second expansion chamber, a like
process occurs whereby the forward velocity of the individual
particles is further decreased and the vapor vortex is further
expanded due to the increased cross sectional area of the second
expansion chamber. The effect of the increase in cross sectional
area on the vortex is the same as that from the expansion in the
first expansion chamber. The second expansion chamber assists in
storing the vapor in the vortex, slows the vortex in its forward
movement and allows creation of greater vorticity when the fluid
reaches the resonant screen, to be described more fully below.
The fluid in the vortex is then impacted on the resonant screen 80
with several resulting effects. The screen resonates to set up a
standing wave pattern in the expansion chambers to assist in
uniformly dispersing particles in the vortex in the second
expansion chamber. It also serves as a drag brake to break up the
remaining particles in the vortex. This is enhanced by the fact
that a force of drag on the fluid flow is more significant than the
force due to the forward momentum of the fluid. Therefore, the
effects due to the drag force predominate over the effect due to
forward flow of the fluid. Additionally, as the vortex impacts the
resonant screen, individual spinning vortices are produced in each
square of the resonant screen due to the appearance to the fluid of
individual bluff bodies oriented perpendicular to each other. There
is also evidence of some vibration in the resonant screen. The
position of the screen relative to the transducer and to the
expansion chambers maximizes resonant effect and standing wave
action, and also the production of the desired particle size, even
after the fluid slows down in the expansion chambers.
The final result, after impingement of the fluid on the resonant
screen is a soft, "warm", low-velocity mist or vapor to be inhaled
by a patient. The mist will have minimal if any impact on the air
passageways in the patient's mouth and lungs as the vapor is
inhaled. The apparent temperature of the aerosol is more acceptable
to the patient also. Additionally, the majority of the liquified
propellant will have expanded to a gaseous state leaving the liquid
droplets of one to three micron monodispersed size at the
monodispersed downstream end of the screen without requiring any
further impingement of the fluid to obtain the desired droplet
size. It is believed that the quality and quantity of output is due
in part to the combined effect of the supersonic and vortical
nature of the transducer output flow and to the resonant screen
function.
It has been found, using a mass spectrometer, that the vaporous
medication output of the inhaler is approximately 98% of the liquid
medication input to the transducer.
The results obtained in the single-inlet transducer combined with
the expansion chambers and resonant screens are reproducible for
any medication delivery canister presently marketed. The same
output is still effected. When the inhaler is manufactured in a
plastic molding process, the inhaler may be disposable after
completion of a medication regimen from one medication canister.
The inhaler is easy to reliably manufacture and easily assembled
with press fit parts. The inhaler is compact and convenient to hold
and carry.
The transducer of the inhaler is inherently self-adjusting and
provides the required particle size output, even with moderate
changes in inlet characteristics. However, a point is reached where
larger flows in the inlet or other fluid changes, such as
propellant-to-liquid ratio, result in a decrease in efficiency of
the inhaler. At that point, the transducer would be changed to
accommodate the different flow characteristics.
There is sufficient air or other gas in the form of nontoxic
propellant and vaporized medication to provide a gas mixture for
inhalation. Entrainment of air by the transducer is not required to
provide an adequate flow rate of medication. However, it is
contemplated that an entrainment valve may be placed behind the
transducer with appropriate changes in the body of the inhaler to
allow entrainment of air by the pressurized fluid.
FIG. 10 shows an alternative embodiment of a transducer in the form
of transducer assembly 156. The transducer assembly has a bore 158
in the form of a parallelopiped and a counterbore 160 in the shape
of a right circular cylinder. Bore 158 extends to transducer
chamber 162 having a converging conical portion 164 formed in the
downstream portion thereof. A first cylindrical aperture 166
extends along the first axis (not shown) toward a second
cylindrical aperture 168 extending along a second axis (not shown)
perpendicular to the first axis. The second axis extends toward a
third axis about which the transducer chamber 162 is oriented. The
second cylindrical aperture extends from the outside surface 170 of
the transducer assembly radially inward slightly past the third
axis. A plug (not shown) is provided for sealing the second
cylindrical aperture 168 to provide a cylindrical aperture similar
to the third cylindrical aperture 142 of FIG. 2. An orifice 172 is
formed coaxial with the third axis from the second cylindrical
aperture 168 to a diverging conical portion 174. The diverging
conical portion is oriented about the third axis. The external
dimensions of the transducer assembly 156 are configured in a
manner similar to the transducer assembly of FIG. 2 for
incorporation into an inhaler.
The transducer assembly includes a tack-shaped bluff body 176
oriented symmetrically about the third axis. The tack-shaped bluff
body includes a cap portion 178 for sealing the transducer chamber
162 and a cylindrical portion 180 tapering downward to the
converging conical portion in the form of a bluff body 164. The
bluff body serves the same function as bluff body 112 described
with respect to FIGS. 1 and 2. The bluff body is preferably tapered
to assist the flow of the resulting vortices in the direction of
the first cylindrical aperture 166.
The transducer assembly 156 is relatively easier to manufacture and
mass produce. For applications other than for medication inhalers,
the preferred material may be different.
The operating characteristics of the transducer assembly 156 are
similar to those described with respect to the transducer of FIG.
2. The dimensions of the transducer can be adjusted to accommodate
different flow conditions for other applications. For example,
where the active ingredient is a liquid having different
characteristics than typical medications, the propellant-to-liquid
ratio may be adjusted. In such case, the dimensions of the bluff
body 176 and apertures 166 and 168 may be modified to provide the
desired flow characteristics in the output fluid. The preferred
configuration, however, is that the pressure change across the
inlet and across the orifice are at or above the critical pressure
ratio for producing supersonic flow in those areas. Additionally,
if different sized particles are desired in the output fluid, the
dimensions and fluid characteristics may be adjusted as
desired.
FIG. 11 shows a nasal adapter 182 in side section for placement
over the resonant screen 80 in the second expansion chamber. This
allows nasal intake of the vaporized medication.
FIG. 12 shows an oral adapter 184 to be positioned over the inhaler
20 in a manner similar to that described with respect to the nasal
adapter of FIG. 11. The oral adapter may be beneficial for
providing medication to infants and patients who may be
incapacitated.
FIG. 13 shows an alternative embodiment of the transducer of FIG.
10 including a propellant canister 188 having an inlet tube 190
coupled to the inlet counterbore 160. The elements in FIG. 13
common to those of FIG. 10 are identified with like reference
numerals and are substantially the same in structure and function
as those described with respect to FIG. 10. A second inlet tube 192
is provided for supplying the active ingredient to the vortex
created through the orifice 172. The inlet tube 192 extends
externally of the transducer 186 to a preferably flexible container
194 for the active ingredient. A guide tube 196 may also be
provided for channeling the flow of the fluid output having a
function similar to the expansion chambers described with respect
to FIGS. 1 and 6.
It is contemplated that the dimensions of transducer 186 are
similar to those of the previously described transducers. The
second inlet tube 192 may have an inside diameter of 40/1000 of an
inch or less.
The function and operation of the transducer 186 up to the point of
the orifice 172 is substantially the same as those described with
respect to the transducers of FIGS. 2 and 10. As there is no liquid
active ingredient entering the transducer from the inlet tube 190,
there are no liquid particles to be atomized. Otherwise, the
creation of the vortices in the propellant is the same as the
production in the transducers of FIGS. 2 and 10. The flow through
the cylindrical apertures is substantially the same.
As the fluid exits the orifice 172, a vacuum is produced at the
outlet of tube 192 due to the supersonic and vortical flow of the
exiting vortex. Additionally, the sub-atmospheric pressure region
in the vortex serves to produce flow of the fluid in container 194
through the tube 192. As the active ingredient leaves the tube 192,
the fluid is effectively atomized by the action of the exiting
vortex. The atomization of the active ingredient is substantially
the same due to the action of the vortex as the atomization with
the transducers previously described.
The propellant canister 188 may be a unit dose canister such as
that described above with respect to FIG. 1 or may be a continuous
flow canister providing output whenever the inlet tube 190 is
depressed with respect to canister 188. In either case, the exiting
vortex produced by the transducer 196 draws the active ingredient
from container 194 as long as propellant is produced from canister
188. During continuous operation of canister 188, the active
ingredient is drawn from flexible container 194 until fluid is no
longer present in the container.
The manipulation of the resulting vortex may be carried out as
desired. For example, the guide tube 196 may be provided with
expansion chambers and resonant screens as discussed with respect
to FIG. 1. Alternatively, if the active ingredient is to be applied
directly from the transducer, the guide tube 196 may be
omitted.
FIG. 14 shows an alternative embodiment of transducer 186 and the
inlet tube 192 wherein the inlet tube is placed external to the
transducer 186 adjacent the outer rim of the diverging conical
portion 174. Substantially the same result can be obtained for
atomizing the active ingredient with the inlet tube 192 located as
shown in FIG. 14 as can be obtained with the arrangement provided
in FIG. 13. The function and operation of the arrangement shown in
FIG. 14 is otherwise the same as that described with respect to
FIG. 13.
FIG. 15 shows an additional embodiment of transducer 186 and the
inlet tube 192 wherein the inlet 192 has its terminal portion flush
with the surface of conical portion 174. The structure and function
of the transducer is otherwise the same as described with respect
to FIGS. 13 and 14.
These transducers are particularly efficient at low liter flows of
oxygen and are very much suited for general hospital use at these
flows with the requisite advantages for low oxygen rate therapy
cited earlier. This capability makes nebulizers built with these
inventions uniquely operable with oxygen concentrators.
It should be noted that the above are preferred configurations but
others are foreseeable. The described embodiments of the invention
are only considered to be preferred and illustrative of the
inventive concept; the scope of the invention is not to be
restricted to such embodiments. Various and numerous other
arrangements may be devised by one skilled in the art without
departing from the spirit and scope of the invention.
* * * * *